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Show 496 [M.P.] firming Building:from Lightning. On the U]? of pointed Conduit": in of the nature and operations of lightning, to ob. fervarions on (och finallexperiments; and that on carefully coma-wing the moi‘t accurate accounts: oi former tiaclsianel the cum-2ft iclatnms of nude that have occurred (mew, the efi'cft'u have iurprrz- inqu agreed with the. theory; it is humbly cun~ ceired that in natural philoiophy, in this branch of it at left, the fuggef‘jon has not {0 much weight; and that the farther newexperimentation! adduced in recommendation of /077g {harp-pomted rods, may have tome claim to credit and conhderation. have been more that have not come to my knowledge. But in every one of thefe, the lightning did 7202‘ fall upon the body aft/J: [202/51, but precifely on the feveral paint; of the rods; and, though the conductors were ibmetimes mffifi41:??th large and romp/eat, was conveyed into the earth, without any material damage to the buildings-Facts then in great, as far as we have them authenticated, juftify the opinion that is 1drayyn from the experiments z'rzfi/m/Z as above re~ It has been urged too, that though points may have confidcrable edicts on afiIM/lprime conductor at null dz/imza'r; yet on grew! clouds and at great (Wilmer; nothing is to be expected from them.-_- To this it is ani'wered, that in thofefmrz/[experiments it is evident the points act at a grcatcrthau the firming dif'rance ; and in the large way, their fervice is only L'xpeflcd where there lsjucé nearuels of the cloud, as to endanger tzflroke; and there, it cannot be doubted the points Inuit have {01116 Cffeét. And if the quantity difcharged by a finglc pointed rod may be to coniiderable 2151 have Ihown it; the quantity ditcharged by a number, W111 be reater, to ortionabl P Blht this pagtff the theory does not depend alone on [mall experiments-Since the practice ofereé}: ing pointed rods in America, (now near 2o years ) five of them have been {truck by lightnmgi VIZ" 3 [About the yen I75 2. E.) 497 Mr. Raven's and Mr. Maine's in South Caroli na Mr. Tucker's in Virginia; Mr. V‘felt's and Mr: Moulder's in Philadelphia. Pollibly there may M!- ate . It has alfo been objected, that unlefs we knew ‘lllllllilllllllllllll‘lll the quantity that might pojflz'é/y be difcharged at M one ftroke from the clouds, we cannot be fure we have providedflficz'mz‘ conductors ; and therefore cannot, depend on their conveying away all that may Fall on their points-Indeed we have nothing to form a judgment by in this cafe but pail fac‘ts; and we know of no inll‘ance where a conga/mt coh- duétor t0 the moiPt earth lam been infuflicient, if half an inch diameter. It is probable that many flrokes of lightning have been conveyed through the common leaden pipes afiixed to houfes to carry down the water from the roof to the ground: and there is no account of fueh pipes being melted and def'rroyed, as muf't fometimes have happened ifthey had been infufiicient.-We can then only judge of the dimenfions proper for S s s a C011- |
